An electro-photographic type image forming apparatus such as a laser printer and an LED printer is known in the prior art. A cartridge is attachable to and detachable from the image forming apparatus. The cartridge is configured to accommodate therein toner.
The number of printable sheets printed by the cartridge is defined as yield information. The image forming apparatus monitors service life of the cartridge on the basis of the yield information. Such image forming apparatus and cartridge are described in the prior art. Further, a cartridge including a detection gear is known in the art. Upon attachment of the cartridge to the image forming apparatus, the detection gear can rotate and a sensor in the image forming apparatus can detect the detection gear as a signal. The image forming apparatus performs determination process as to whether the cartridge is a new cartridge and/or the image forming apparatus obtains yield information on the basis of the signal obtained from the sensor.